1. Field of the Invention
The present invention relates to a hard disk drive (HDD) defect list searching method, and more particularly, to an HDD defect list searching method which reduces the number of times a defect list is referred to by storing defect information of a target track and information on a next defective track and using the defect information of the target track and the information on the next defective track the next time the defect list is searched for.
2. Description of the Related Art
A hard disk drive (HDD) is a magnetic recording medium on which data can be recorded and is comprised of a plurality of circular disks, i.e., media. Data are recorded along tracks, which are concentric circles formed on the surface of a disk. Each track on the surface of a disk is divided into blocks, which are called sectors, so that data can be systematically recorded on the disk and data already recorded on the disk can be systematically searched for. Information on the location of each of the sectors is represented by specific identifiers, such as a cylinder or track number, a head for recording/reproducing data on/from a data storage medium by accessing the data storage medium, and a sector number.
A disk is rotated by a spindle motor, and data are recorded on and reproduced from the disk by read and write heads provided at an actuator arm.
Sometimes, a disk may have a defective region on which data cannot be recorded and from which data cannot be reproduced.
For example, when loading an actuator assembly onto a medium during the manufacture of an HDD, the medium may get some scratches, which causes defects.
Physical damage to the surface of the medium caused by scratches causes a loss of a number of bytes, which are basic units of data recorded on and/or reproduced from the medium. Since a disk is controlled on a sector basis or on a track basis, a defect caused by a scratch on the surface of the disk affects at least one sector.
Defective sectors cannot store data. Accordingly, it is important to provide an HDD which does not seem to have any defective sectors, to a user by searching the HDD for defective sectors and replacing the defective sectors with normal sectors during the manufacture of the HDD.
During the manufacture of an HDD, a burn-in test is performed. The burn-in test is used to figure out whether or not and where a defect has occurred on a disk by performing read and write tests on the entire region of the disk while changing data patterns and read and write conditions by deliberately deviating a head from tracks of the disk or while changing read and write channel parameters. The location of the defect on the disk is represented by a cylinder number, a head number, and a sector number. The identified location of the defect and an error code are written on a defect list or a slip list so that a user can be prevented from accessing the place where the defect has occurred. This defect list searching method is disclosed in Korean Patent Laid-open Publication No. 1999-65700 published on Aug. 5, 1999.
Even though discontinuity exists in sectors due to some defective sectors, sector addresses, which are necessary to access the sectors, must be consecutively provided. Accordingly, a process of replacing defective sectors with normal sectors in a spare region is necessary, and this process is called defect management.
There are two different defect managing methods, i.e., a slip method and a reassign method.
The slip method is mainly used to manage defects on a disk, which are detected in a burn-in test, and the reassign method is mainly used to manage defects occurring during a user's use of an HDD.
The two defect managing methods are similar in that defective sectors are replaced using a spare region but are different in the way they use the spare region when replacing the defective sectors. Specifically, in the slip method, defective sectors in a data region are replaced by their adjacent sectors in the data region, and then in the end, as many sectors as the number of defective sectors in the data region are compensated for by sectors in a spare region. On the other hand, in the reassign method, defective sectors in the data region are replaced by sectors in the spare region. These two defect managing methods are respectively disclosed in Japanese Patent Laid-open Publication No. 2002-63767 (published on Feb. 28, 2002) and Korean Patent Laid-open Publication No. 2001-2478 (published on Jan. 15, 2001).
In a case where data are recorded on and/or reproduced from a disk by an external device, such as a host computer, which accesses an HDD, the HDD obtains defect information indicating whether or not a target track includes defective sectors and how many defective sectors the target track has, by referring to a defect list recorded in a system region of the disk, and generates sector addresses necessary to access sectors of the target track by referring to the defect information. This defect searching method is disclosed in Japanese Patent Laid-open Publication No. 1993-28651 (published on Feb. 5, 1993) and Korean Patent Laid-open Publication No. 1999-28007 (published on Apr. 15, 1999).
However, in the conventional defect list searching methods, whenever a host computer accesses an HDD, the host computer has to search for defect information on the entire tracks of a disk by referring to a defect list, and requires many additional operations of the HDD and delays access to data.